Formation of electric spark WC-Co coatings with modifying Cr2O3 additives

Abstract

Tungsten carbide coatings are widely used on steels due to their high hardness and wear resistance, but they have low high-temperature oxidation resistance and therefore need to be modified with oxidation resistance compounds. Electrode materials based on WC-8 %Co with addition of 1, 3 and 6 wt.% Cr2O3 were prepared by powder metallurgy for the deposition of electric spark coatings on steel 1035. An increase in the content of Cr2O3 in electrodes led to a rise in the thickness of the coatings from 18.2 to 28.3 µm. The tungsten semicarbide phase dominated in the structure of the coatings. The concentration of chromium in the coatings is a function of it in the electrodes. Polarization tests of coated samples showed an increase in the corrosion potential and a decrease in the corrosion current density with an increase of Cr2O3 concentration in WC-Co electrodes. The Cr2O3 additions into the WC-8 %Co electrode allow increasing the oxidation resistance of coatings at a temperature of 700°C. The coating microhardness increased monotonically from 9.6 to 13 GPa, the friction coefficient decreased from 0.7 to 0.58, and wear rate decreased with increasing Cr2O3 content. Electric spark deposition of the WC-8 %Co electrode with addition of Cr2O3 on steel 1035 allows increasing its wear resistance up to 14 times.